Masterpiece Theater: Energy Kills

In the most recent physics unit, we learned various things about energy. We learned that energy can be transfered from one object to another and has the ability to bring about change. Perhaps most importantly, we learned that energy is conserved from initial to final states. This means that unless work is done, initial energy will be equal to final energy due to energy conservation. Energy can't disappear, it can only transfer to other objects through work, such as applied energy (initial state) and friction (final state). The three types of energy we learned about were potential energy, kinetic energy, and elastic energy. Potential energy usually refers to potential energy due to gravity, kinetic energy occurs when an object is in motion, and elastic energy occurs when energy is stored in an object with elastic tendencies, such as springs and bouncy balls. The method of energy transfer we learned about is work. Energy is transferred when energy enters or exits a system. We learned how to draw bar graphs and energy flow diagrams to represent the type of energy present in a system.
Work represents the amount of change a force produces when it acts on an object, and is equated as W=FX, if the force is acting in the same direction as x. If F and X are perpendicular, then no work is done. Power is the rate at which work is performed, and P=W/T.
Kinetic energy is equal to 1/2mv^2. Potential energy is equal to mgh. Elastic potential energy is equal to 1/2kx^2, with k representing the spring constant. We also learned that the net work performed on a body is equal to the difference between initial and final energies, and that mechanical energy is equal to the sum of the potential and kinetic energy found in a system.
Now that the knowledge base has been etablished, I will delight my readers with a thrilling
tale of physics.

"Edith, I'm sure you know why I've called you here today," said Edgar, a curmudgeonly old
coot.
"Yes," answered Edith, thinking that Edgar would finally grant the monastery a much needed donation. After all, he had no family, and obviously no friends, so he might as well grant a portion of his vast fortune to her church, which had fallen on hard times.
"Well, the rest is just business then. Shall we go for a stroll among the gardenias and discuss it?" asked Edgar.
"Yes, I do so adore gardenias," answered Edith, humoring the man until he bequeathed his
fortune to the church that had been soliciting him for so long.

During their stroll, Edgar and Edith chatted congenially, both of them waiting for the right moment to bring up their respective thoughts.
When they reached the edge of a cliff that lay at the edge of Edgar's enormous estate, they stopped to begin their conversation.

"As you know," began Edgar, "I have been diligently conserving my resources in order to use them to their best affect."
"Indeed," interrupted Edith, "and the brothers and sisters at the monastery would certainly bless you in their prayers and feel undying gratitude if you took upon yourself to fund our missionary ventures."
"Yes," answered Edgar, "but I have been thinking that my resources could be used to produce a much more drastic and immediate effect if I transferred them to you." And with that, Edgar proceeded to transfer his energy to Edith in a most drastic manner, by pushing her off of the cliff.

intial energy = final energy, or PEga+W=PEgb+KEb

Please note that there is no air resistance due to the presence of sharks.*
*This has yet to be proven due to lack if government funding.

Energy on Prezi

Redemption: Uniform Circular Motion and Universal Gravitation

Lately, our physics class has been learning about the motion of objects in a circle, and the force of gravity. In the unit over uniform circular motion (hence the title), we learned about centripetal force, how to calculate the tangential velocity, the centripetal acceleration, period, and frequency. In uniform circular motion, an object moves around the perimeter of a circle with a constant speed. The time it takes to travel one rotation around the circle is known as the period, and frequency is the number of revolutions that an object can travel during a certain time period. Centripetal force is the force that keeps the object moving in a circle. Centripetal force is always pointed toward the center of the circle, and is equal to an object's mass multiplied by its velocity squared divided by the radius of the circle that the object is traveling around.
Universal gravitation is the law that proposes that all objects in the universe are attracted to all other objects in the universe. The force of this attraction can be determined by the multiplying the product of the masses with the value of G (6.67 E -11) and then dividing this by the square of the distance between the two objects.
The area of the unit that I had the most trouble with was identifying the centripetal force. The reason I had trouble with this is because I tend to over think things, and often confused other forces with the centripetal force. In order to overcome this difficulty, I just needed to remember that centripetal force is the only force pointing toward the center of the object's circular route. In order to remind myself which force is the centripetal force, I drew sketches of the situation described in each problem. For instance, if a rock is being swung around on the end of a string, the centripetal force is provided by the string, so the tension force supplies the centripetal force. And, for a change, I didn't have any outstanding problems with universal gravitation.

This unit of physics has many practical uses. One such use could be gaining respect and eventually power from your peers through your superior knowledge of physics. For instance, if you are rounding a corner with your friends in the car, and your dashboard hula dancer slides away from where it was lovingly placed, slipping toward the precarious edge of the dashboard, you will know what's going on. One of your friends, awed by this phenomenon, asks why the hula hooping doll seems so attracted to the edge of the car. You, with your extensive physics knowledge,  are able to answer, "The doll lacks a source of centripetal force, and continues moving in the same direction it was moving in before the car turned." Your friend responds by saying, "Oh, yeah. I totally knew that," but secretly admiring you because they did not, in fact, know that. Later, when said friend conquers the world, they will grant you a high ranking government position, even though you aren't really qualified and have been dodging the international authorities for years. Effectively, you will be granted a life of riches, power, and diplomatic immunity, all because you knew the inner workings of centripetal force.
Or you could figure out the coefficient of static friction of tires against asphalt while you're on a mind numbingly boring road trip. Universal gravitation can be used to find out how attracted you really are to your significant other. (If your mass is 100 kg, and your boyfriend's mass is 150 kg, and y'all are sitting two meters apart, then you are .000000250125 N attracted to him. That's not very much. Maybe y'all should break up.)

Either way, it's pretty useful.

Mythbusters

In this episode of Mythbusters, we (Abigail, Tori, Sabeeh, and Will) fearlessly set out to disprove wrongly believed physics myths. We gallantly disproved these myths in order to  preserve physics' integrity and save lives. After all, misunderstanding science can be dangerous.


Myth 1:
The first wrongly accepted myth is stated thus: An object always moves in the direction of the net force exerted on it.
This is false. An object usually moves in the direction of this force exerted on it , but not always. If an object always moves in the direction of the net force exerted on it, and we throw a basketball on the ground, then it won't bounce back into the air, because gravity would be the only force acting on the basketball. To disprove this myth, the bold mythbusting team threw a basketball at the ground, from whence it proceeded to bounce back into the air. This is a classic example of projectile motion.

The forces acting on the basketball after it bounces look like this:

As you can see in this sum of the forces, the only force acting on the basketball while it's in the air is gravity. (The unattached arrow represents direction.)

 According to the false myth, the basketball should be falling faster than the wreckage of a sky pirate ship. In fact, if the myth was true, the ball wouldn't have gotten off the ground at all. Because the basketball is moving up, the myth is busted.


Myth 2:
The second myth is theorized so: An object always changes its motion if there is a force exerted on it by other objects.
This myth is also false. Most objects change their direction when there is an outside force exerted on it, but some objects just ignore outside forces and keep going. If an object always changes its motion if there is a force exerted on it by other objects, and a ball has normal force exerted on it by a tube then it will change directions. Once again, the intrepid group of mythbuster set out to disprove a myth. This time, we rolled a basketball at an empty, defenseless tennis ball tube.

Proof!:

When the basketball hits the empty tennis ball tube, it ignores it like a steamroller ignores a squirrel. The FBD of ignorance that strong looks like this:

(The unattached arrow represents direction.)
The empty tennis ball tube exerts a normal force on the basketball when the basketball hits it, as shown in this sum of the forces acting on the basketball:

Even though there is a force acting on the basketball, its motion isn't affected in any way whatsoever, rendering the myth busted.


Termination (it's a legitimate synonym for conclusion):

In the end, my troops and I did what we set out to do. We disproved myths. In fact, we did so well, that we disproved all of the myths!

Now, you may be asking yourself, 'If these myths were so quickly disproved by a motley crew of high school freshman, why would the human population in general believe them?' My answer to you is this: they don't. The human population in general doesn't think about physics, probably because it's the most mindblowingly awesome subject ever. But if the world did hypothetically think about physics all the time, they might still believe these myths.
But why? Is it because human ignorance is as flagrantly obvious as a volcano full of molten lava in your face? (I really hope that never happens to anyone. It would be really painful.) I don't think ignorance is the problem. The birth of these myths is rooted in misguided logic. I mean, they sound pretty reasonable.
The first myth's origins are obvious. The hypothetical, misguided physics geniuses (genii only applies to spirits, demons and qualities) construct FBDs of their daily movements, and they notice that whenever they exert a force, they move in that direction (walking, running, swimming, skating, snowboarding). However, these physics geniuses didn't continue to construct FBDs for all of the other aspects of their lives, or they quickly would have realized that their theory was wrong.
The second myth also seems like common sense. When you run into something, like a sumo wrestler or a giant cube of jello, you tend to bounce off. The prodigies of the hypothetical physics world were quick to figure out that your motion changed because the sumo wrestler and the jello exerted a force on you. Or maybe they just played pool frequently. In any case, the fault in this theory was that they weren't empathetic enough. If they had put themselves in the sumo wrestler's shoes, or the jello's shoes, they would have known that they didn't move at all.
The laughable physics geniuses' foibles live on in the mind of real people, ones who don't really construct FBDs for every situation. This is why the masked crusaders, known only as the 'Mythbusters', continue to redistribute the wealth of knowledge.